Three-dimensional printing, also known as additive manufacturing, is a process of making a three-dimensional solid object from a digital model of virtually any shape. Many three-dimensional printing technologies use an additive process in which an additive manufacturing device forms successive layers of the part on top of previously deposited layers. Some of these technologies use inkjet printing, where one or more printheads eject successive layers of material. Three-dimensional printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
Additive manufacturing systems can produce a wide range of items with some proposed uses including encapsulation of chemicals in soluble substrates for the delivery of medications or more broadly to chemical delivery devices. The additive manufacturing system deposits an “active chemical” in the chemical delivery device that is suspended in an excipient material of a substrate that dissolves in a solvent. As used herein, the term “active chemical” refers to any chemical that is embedded within a chemical delivery device for controlled release over time as the chemical delivery device dissolves in a solvent. As used herein, the term “excipient material” refers to one or more types of material that form a structure of a chemical delivery device, encapsulate one or more active chemicals, and control the release of the active chemicals within the chemical delivery device as the chemical delivery device dissolves in a solvent or melts in a temperature-controlled chemical release process. In many embodiments, the excipient materials are substantially non-reactive with the active chemical, but the excipient materials are soluble in some form of solvent that dissolves the chemical delivery device to emit the active chemical during use of the chemical delivery device. Excipient substrate materials are known to the art that dissolve in various solvents including water, acids, bases, polar and non-polar solvents, or any other suitable solvent for different applications. Corn starch and microcrystalline cellulose are two examples of materials that are commonly used as excipient materials for an active chemical ingredient, although other materials include gelatins, polymers, including UV-curable polymers, and the like that are used in various chemical delivery devices. Some forms of excipient material dissolve to deliver the active chemical by melting or otherwise disintegrating at an operating temperature, such as an elevated melting temperature that is higher than the typical ambient storage temperature for the chemical delivery device.
As the substrate dissolves, the active chemical releases into a medium around the chemical delivery device and produces a chemical reaction. Applications for such devices include, but are not limited to, medicament delivery in human and veterinary medicine, fertilizer and pesticide delivery for agriculture and horticulture, dye release for tracking the flow of water or other fluids, and delivery of an active chemical in an industrial process.
While prior art additive manufacturing systems can produce chemical delivery devices, some forms of chemical delivery devices require additional structural elements for proper operation. For example, some time-release chemical delivery devices require a specific concentration gradient of an active chemical to deliver a dose of the active chemical that varies over time. In some instances, the tablet does not deliver the active chemical at a desired rate if the active chemical is distributed within the volume of the tablet in a non-uniform manner. For example, the rate of release from the tablet can be too high at some points during the dissolving of the tablet when it delivers a larger concentration of the active chemical than intended. Also, the rate of release can be too low when the tablet delivers too low of a concentration of the active chemical at particular point in time after it is digested. Additionally, some tablets include two or more types of active chemicals that should not mix while in the tablet, but should mix once the tablet dissolves. Consequently, improvements to additive manufacturing processes and systems that enable production of tablets with precise distributions of active chemicals would be beneficial.